To carry on the preferred operations wrapping machines with film include many mechanisms, the purpose of this invention deals with the mechanism in charge of determining the amount of film that is needed in each different process, depending of the product that is going to be wrapped up.
On the European Patent of Invention number 0092758, which priority corresponds to U.S. Pat. No. 371,892, between other parts from wrapping machines with film, it is claimed a to and fro mechanism that can be adjusted based upon the size of the product to be wrapped, using a lever jointed at one of its ends to a lower plate, while at the upper end of the lever is a jointed connecting rod with curved shape, that by one of its ends is linked to a tensor and at its other end moves through a pivot, in an arched slot found in the lower plate, being forecast that the original lever, that is jointed to the chassis of the machine, will have a lateral pivot linked to a cam which in turn produces the swinging and/or the to and fro movement of that lever, and in consequence to the swinging of the curved rod, and establishing on the end a tensor that joints the holding mechanisms for the end of the film, with the purpose of driving it and to perform, with other apropiate mechanisms, the wrapping, cutting and other operations that take place inside of the machine as a whole.
The lower plate, equipped with the curved slot on wich the lower end of the tensor moves, is jointed to a mechanism of longitudinal modification of the mention plate, and so of the tensor placement, in such a way that when the tensor changes, the top position on which the curved connecting rod moves also changes and thereby changing its to and fro movement, changing with it the distance of the sheet of the film.
It must be considered that the adjustment of the length of the curved end of the curved connecting rod will be realized when the length of the film must be changed, because it requires to wrap up a new product. In that sense, the mechanisms of the transmissions of the adjustements mentioned, will only act when the length of the film must be changed, to wrap up another new product.